Raindrops over glass

riot · Apr 2013

Hi! I have been trying to figure out how to simulate some raindrops sliding on a window in 3Ds Max so I can bake out a normalmap for UDK but I have had no luck. Do you have any suggestions on how I could create a normalmap for raindrops to use inside UDK? I am trying to achieve something like this: http://youtu.be/a3ZYBmCLfaI?t=19s
For that I guess I need 2 or 3 lerped different raindrop normalmaps which will have some distortion and a panner, I guess, and that way they will move.

Mark Dygert · Apr 2013

RealFlow would be perfect for that, but probably cost prohibative... $3k ouch.

You could probably do something similar with the standard 3dsmax particle system (just not going to get some of the cooler dynamic effects you get with RealFlow). Still with a U-Deflector a Super Spray and some Drag you can throw some particles on a plane and have them run down, maybe even spawning a trail as it does. You could also hand animate the drops if you aren't familiar with particle flow.

Amsterdam Hilton Hotel · Apr 2013

Mark Dygert wrote: »

You could also hand animate the drops if you aren't familiar with particle flow.

and maybe even without particles, trails could still be achieved by overlaying the most recent x frames, with increasingly reduced opacity, over the current one? or even a lot of motion blur in the render..? could be interesting, but maybe a waste of time if there's just a straight way to simulate it I guess

RezNik · Apr 2013

This might sound kinda crazy, but if you could create a raindrop and use the Hair and fur modifier to place the drops on the plane using the "instanced node" under the tools roll out(in the hair and fur modifier) this would give you access to several randomizing parameters. You would probably have to paint the trails in though.

Mark Dygert · Apr 2013

Amsterdam Hilton Hotel wrote: »

and maybe even without particles, trails could still be achieved by overlaying the most recent x frames, with increasingly reduced opacity, over the current one? or even a lot of motion blur in the render..? could be interesting, but maybe a waste of time if there's just a straight way to simulate it I guess

That might work.

RealFlow would solve the problem of drops running into each other, growing and shrinking as volume is lost and added, as well as the water running down the trail, thinning out and disappearing.

You could hand animate one drop/trail and copy it a few times.

This might sound kinda crazy, but if you could create a raindrop and use the Hair and fur modifier to place the drops on the plane using the "instanced node" under the tools roll out(in the hair and fur modifier) this would give you access to several randomizing parameters. You would probably have to paint the trails in though.

That could work, the particle system has the ability to "Birth particles" over the surface of an object randomly using a "Position Object" instead of the standard Position. This gets used for all kinds of things, putting leaves on trees, scattering rocks, plants, bushes and debris bla bla bla...

You can also use object paint to scatter objects on the surface too. Then you can simulate.

riot · Apr 2013

Wow, this is indeed harder than I thought. I have found a tutorial on how to do a particle system for raindrops on glass, but those particles are just straight lines, therefore I can't bake a normalmap from them. I guess that there may be some way to attach meshes on those lines, so I'll have to test it out. If this doesn't work I'll try RezNik's solution, because it may work really good. But first I will try to do it in Realflow as Mark said, $3k is way too much for me, but luckily they have a demo version so I'll give it a try. Thanks everyone, I'll come back with the results soon.

JParkerRH · Apr 2013

Heya Riot...you could also hand-paint different rain paths and use a black & white gradient ramp to drive a lerp giving you the illusion of motion. If you stacked a few of these with different timings blending them in & out I think you'd get a fairly convincing effect of the water streaming down the window.

I'd probably mix that with a particle system on the window though, spawning "drops" hitting the window and generating a spawn event as it slithers down the window pane for the watery trail behind it. I've done that for blood splatter sliding down the camera and it's worked really, really well.

Combining these two, the particles will help convince the viewer that the whole thing is a dynamic solution.

riot · Apr 2013

Okay, I've finally managed to do it. It took me a while, but it's done. I had to go with the max particles way because Realflow was just too complicated to work with. I created a particle system like in the tutorial that I have posted above and then I've converted the particles into spheres. Then, with the help of the mesher modifier I've coverted them to edit. poly, baked them as a normalmap and created the material in UDK. It's not the best motion-wise, but it looks pretty good, better than I was expecting it to look: image
Anyway, thanks to all of you for your suggestions, you helped me a lot. Problem solved

sprunghunt · Apr 2013

riot wrote: »

Wow, this is indeed harder than I thought. I have found a tutorial on how to do a particle system for raindrops on glass, but those particles are just straight lines, therefore I can't bake a normalmap from them. I guess that there may be some way to attach meshes on those lines, so I'll have to test it out. If this doesn't work I'll try RezNik's solution, because it may work really good. But first I will try to do it in Realflow as Mark said, $3k is way too much for me, but luckily they have a demo version so I'll give it a try. Thanks everyone, I'll come back with the results soon.

if you use a superspray particle system you should be able to set the particle type to "metaparticles" These should be pretty convincing water droplets.

Or try using a blobmesh linked to particles - or any other kind of geometry.

http://docs.autodesk.com/3DSMAX/15/ENU/3ds-Max-Help/index.html?url=files/GUID-4189F2D5-62CE-43E6-8DDB-BF5FB79EB557.htm,topicNumber=d30e47119

Raindrops over glass

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